The Afghan Health Ministry says the number of people killed in an attack on a Shi’ite mosque in the capital Kabul, has risen to 28, up from 20.

Health ministry spokesman Mohammad Ismail Kawoosi said more than 50 were also wounded, including over a dozen women and children, in the hours-long attack on August 25.

Mohammad Salim Rasuli, chief of Kabul's hospitals, confirmed the latest death toll and said the number of casualties could still rise.

The Islamic State (IS) extremist group, which has targeted the country's Shi'a minority with deadly attacks in recent years, claimed responsibility for the attack.

Police said two suicide bombers blew themselves up at the entrance of the Imam Zaman Mosque in Kabul’s Qala-e Najara area. Two other attackers who stormed the building were later shot by security forces.

The United Nations Assistance Mission in Afghanistan (UNAMA) and Human Rights Watch strongly condemned the attack.

“This latest in a series of attacks targeting members of the Shi’a community at worship has no possible justification,” said Toby Lanzer, the UN Secretary-General’s Deputy Special Representative for Afghanistan and acting head of UNAMA, on August 26.

“Such attacks directed against congregations and places of worship are serious violations of international law that may amount to war crimes,” he added.

In a statement on August 25, Human Rights Watch said the attack was “a serious violation of the laws of war, and an apparent war crime.”

The attack took place when worshippers had gathered for Friday prayers.

Danish said two police officers were among the dead.

A cleric who was leading the service in the mosque was among those killed.

The IS-linked Amaq news agency said the group’s affiliate in Afghanistan claimed responsibility for the attack.

Shi’a are a minority in Afghanistan who have been threatened and attacked in the past by various Sunni militant groups -- including IS and Taliban extremists.

Last month, IS militants attacked the Iraqi Embassy in Kabul that killed two local employees and later threatened to attack Shi’ite places of worship in Afghanistan.

And on August 1, at least 32 people were killed and more than 60 injured by a suicide bomber and a gunman who targeted a Shi’ite mosque in the western city of Herat in an attack claimed by the IS group.

The August 25 assault comes after President Donald Trump outlined earlier this week the new U.S. strategy for the war-torn country.

It also underscores increased insecurity in Afghanistan as a resurgent Taliban steps up offensives across the country.